Cable telecommunications systems, sometimes referred to as broadband communication systems (BCSs), have been known for a number of years and are currently gaining in popularity and coverage for the distribution of television programming, telephone service and networking of computers such as providing Internet access since they can carry many signals over a wide bandwidth with little, if any interference or distortion, particularly as data transmission rates have increased to accommodate high definition television, increased volume of digital communication and the like. By the same token, since these communications are intended to be confined within the cable system, the increased bandwidth required for such communications need not be allocated from the available bandwidth for other communications such as radio, navigation, GPS, emergency communications and the like which must be transmitted as free-space electromagnetic waves through the environment. However, flaws in cable shielding in cable telecommunication systems can allow signal egress which can potentially interfere with free-space broadcast communications and potentially cause hazards. Reciprocally, flaws in cable shielding can permit signal ingress into the cable from the environment and degrade or interfere with the signal being carried by the cable telecommunication system. Therefore, such flaws must be quickly discovered and remedied as they occur due to weather, mechanical damage or the like. Such monitoring is generally performed by permanently installing signal leakage receivers and global positioning system receivers in BCS service vehicles which will normally cover a substantial portion of the service area in a relatively short period of time while executing work orders for installations and repairs of the BCS. The location of the service vehicle is constantly monitored and reported. When an egress signal of significant signal level is detected, the vehicle location and egress signal strength can be recorded or automatically reported and appropriate work orders issued to correct any such shielding flaw.
Since a broadband communication system signal leaking from a shielding flaw has the potential for interference with free-space communication signals, broadband communications systems are subject to federal regulations and continuous monitoring and periodic reporting is required. Specifically, a BCS operators must identify leakage signal amplitudes for all leaks and to identify the service or plant area covered during a given time period and to insert such information into an equation such as
  CLI  =      10    *                  log        10            ⁡              (                              1            φ                    ⁢                                    ∑                              i                =                1                            n                        ⁢                          E              i              2                                      )            in which:
φ=percentage or fraction of the plant/service area covered,
i=number of qualified leakage elements, and
E=qualified leakage measured signal level.
The value of this equation is referred to as the cumulative leakage index (CLI) which must be reported periodically (e.g. quarterly) and reports leakage above a threshold strength actually discovered in an area of the BCS plant by inspection projected over the entire service area of the BCS plant. That is, if 75% of the BCS plant was inspected during an inspection period, the value of 1/φ in the equation would be 1/0.75 or 1.333. Such an equation sums the square of all detected shielding flaws having a radiated signal level above a given value (e.g. greater than 50 μV per meter to be “qualified” for reporting) and effectively normalizes, averages or projects that total radiated power over the entire BCS plant by the proportion of the plant or service area covered by inspection during a given period of time. The proportion of plant or service area covered must be at least 75%. The CLI is thus a projected measure of the total radiated power from shielding flaws over the entire BCS plant and is thus an approximate measure or figure of merit of the overall shielding quality or condition of the BCS. Such a computation is generally performed more or less continuously on a rolling basis such that the time period covered is substantially constant.
However, while egress signal level can be measured with substantial accuracy, such a computation can be significantly affected by the technique used to approximate φ, the proportion of the service area that is covered by service vehicles that are providing automatic inspection of the BCS for egress signal leakage through shielding flaws. Since different techniques can be used to approximate both the area covered by inspections and the overall total service area of the BCS system plant (e.g. signal distribution area) and the installation of a given BCS plant may not be uniform over the geographical extent of the service area, computed CLI values may vary greatly for a given BCS plant, depending on the regions of the plant actually inspected, even if the approximation is consistently performed, and comparison of CLI values between different BCS plants is not particularly meaningful.